Within a corporate environment, telephone service is typically provided by a private branch exchange switch. A private brunch exchange switch is an on-site facility, that is typically owned or leased by a company or another entity. The private branch exchange interconnects the telephones within the facility and provides access to the public telephone system. Typically, a private branch exchange environment uses digital telephone terminals and digital switching. Digital private branch exchange switches were designed to handle analog voice traffic, with the switch performing an analog-to-digital conversion (DAC) so that digital switching can be used internally on the entity premises. Increasingly, however, private branch exchanges (PBX) are carrying data traffic as well as voice traffic. Typically, data calls are generally switched through a modem-pool to the private branch exchange for transmission to the Public Switched Telephone Network (PSTN).
While a private branch exchange allows an entity to efficiently provide access to communication services without necessarily having dedicated telephone lines for each employee, the private branch exchange often limits the types of communications equipment that may be connected to the PBX and the types of services that may be accessed over the PBX. For example, since the telephone terminals connected to the PBX are digital, it is often difficult, if not impossible, to connect an analog device to the PBX. In addition, the communications protocols and hardware specifications of a given private branch exchange are often proprietary to the manufacturer of the PBX. Thus, it is often difficult, if not impossible, to connect equipment manufactured by another manufacturer to the PBX.
Adjunct processors have been proposed for use with private branch exchanges (PBXs) to supplement and enhance the telecommunications services provided by the PBX. For example, a voice mail system is often used with a PBX to provide users with voice messaging capabilities. In order to work together, the PBX and the adjunct processor must be able to communicate with each other. This is typically accomplished by means of a digital control data link, such as the DCIU link, commercially available from AT&T, that interconnects the PBX control processor with the adjunct processor.
In addition, other interfaces have been proposed or suggested that allow other types of equipment to be connected to a private branch exchange. For example, the 8411 terminal, commercially available from Lucent Technologies Inc., of Murray Hill, N.J., provides a tip/ring interface that allows analog devices to be connected to the private branch exchange and an RS-232 (passageway) interface that allows a computer to be connected to the PBX and permits Computer Telephone Integration (CTI). These other interfaces, however, including the 8411 terminal, are typically designed specifically to provide specific features and to operate with the particular communications protocol and/or hardware specification of a given private branch exchange manufacturer, or telephone terminal manufacturer. Current interfaces are unable to support additional features that may be desired by a customer.
As apparent from the above-described deficiencies with conventional techniques for connecting devices to a private branch exchange switch, a need exists for a standard interface to the private branch exchange that allows one or more modules to access voice or data channels on the private branch exchange. A further need exists for an interface to the private branch exchange that utilizes an integrated digital telephone chip. Yet another need exists for an interface to the private branch exchange that permits a module to support additional features for the private branch exchange.